1561865004 has 252 divisors, whose sum is σ = 5055352344. Its totient is φ = 419344128.

The previous prime is 1561864991. The next prime is 1561865047. The reversal of 1561865004 is 4005681651.

1561865004 is a `hidden beast` number, since 15 + 61 + 86 + 500 + 4 = 666.

It is a tau number, because it is divible by the number of its divisors (252).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 1561865004.

It is an unprimeable number.

It is a polite number, since it can be written in 83 ways as a sum of consecutive naturals, for example, 2428707 + ... + 2429349.

It is an arithmetic number, because the mean of its divisors is an integer number (20060922).

Almost surely, 2^1561865004 is an apocalyptic number.

1561865004 is a gapful number since it is divisible by the number (14) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1561865004, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2527676172).

1561865004 is an abundant number, since it is smaller than the sum of its proper divisors (3493487340).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1561865004 is a wasteful number, since it uses less digits than its factorization.

1561865004 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 696 (or 672 counting only the distinct ones).

The product of its (nonzero) digits is 28800, while the sum is 36.

The square root of 1561865004 is about 39520.4378012188. The cubic root of 1561865004 is about 1160.2399929523.

The spelling of 1561865004 in words is "one billion, five hundred sixty-one million, eight hundred sixty-five thousand, four".